Combined crossing termination shunt and railroad crossing control system

ABSTRACT

A railroad crossing control system includes a grade crossing predictor system or grade crossing motion system with a combined crossing termination shunt, the combined crossing termination shunt including a housing, a first printed circuit board (PCB) comprising first circuitry and first rail terminals, a second printed circuit board (PCB) comprising second circuitry and second rail terminals, wherein the first PCB and the second PCB are positioned inside the housing, and wherein the first circuitry and the second circuitry are configured for a same frequency.

BACKGROUND 1. Field

Aspects of the present disclosure generally relate to railroad crossing control systems including railroad signal control equipment such as for example a grade crossing predictor system and a crossing termination shunt.

2. Description of the Related Art

Railroad signal control equipment includes for example a constant warning time device, also referred to as a grade crossing predictor (GCP) in the U.S. or a level crossing predictor in the U.K., which is an electronic device that is connected to rails of a railroad track and is configured to detect the presence of an approaching train and determine its speed and distance from a crossing, i.e., a location at which the tracks cross a road, sidewalk or other surface used by moving objects. The constant warning time device will use this information to generate a constant warning time signal for a crossing warning device.

A crossing warning device is a device that warns of the approach of a train at a crossing, examples of which include crossing gate arms, crossing lights (such as the red flashing lights often found at highway grade crossings in conjunction with the crossing gate arms discussed above), and/or crossing bells or other audio alarm devices. Constant warning time devices are typically configured to activate the crossing warning device(s) at a fixed time, also referred to as warning time (WT), which can be for example 30 seconds, prior to the approaching train arriving at the crossing.

Typical constant warning time devices include a transmitter that transmits a signal over a circuit, herein referred to as track circuit, formed by the track's rails, for example electric current in the rails, and one or more termination shunts positioned at desired approach distances, also referred to as approach lengths, from the transmitter, a receiver that detects one or more resulting signal characteristics, and a logic circuit such as a microprocessor or hardwired logic that detects the presence of a train and determines its speed and distance from the crossing. The approach length depends on the maximum allowable speed (MAS) of a train, the desired WT, and a safety factor.

Termination shunts or devices include for example hardwire shunts, wide-band shunts, and narrow-band shunts. Depending on a frequency used and existing ballast conditions at a specific grade crossing, an efficacy of a termination shunt may vary. For example, lower frequencies, e.g. 86 Hz, can create situations where an approach is not fully terminated by the termination shunt, resulting in the system, e.g. predictor and/or motion system, to look beyond the intended point of termination.

SUMMARY

Briefly described, aspects of the present disclosure relate to a railroad crossing control systems including railroad signal control equipment comprising for example a grade crossing predictor (GCP) system, and a crossing termination shunt utilized within such a railroad crossing control system.

A first aspect of the present disclosure provides a combined crossing termination shunt comprising a housing, a first printed circuit board (PCB) comprising first circuitry and first rail terminals, a second printed circuit board (PCB) comprising second circuitry and second rail terminals, wherein the first PCB and the second PCB are positioned inside the housing, and wherein the first circuitry and the second circuitry are configured for a same frequency.

A second aspect of the present disclosure provides a railroad crossing control system comprising a grade crossing predictor system or grade crossing motion system comprising at least one combined crossing termination shunt, the at least one combined crossing termination shunt comprising a housing, a first printed circuit board (PCB) comprising first circuitry and first rail terminals, a second printed circuit board (PCB) comprising second circuitry and second rail terminals, wherein the first PCB and the second PCB are positioned inside the housing, and wherein the first circuitry and the second circuitry are configured for a same frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a highway-rail grade crossing warning system at a grade crossing in accordance with an exemplary embodiment of the present disclosure.

FIG. 2 and FIG. 3 are schematic diagrams illustrating first and second embodiments of a crossing termination shunt in accordance with an exemplary embodiment of the present disclosure.

FIG. 4 and FIG. 5 are schematic diagrams illustrating third and fourth embodiments of a crossing termination shunt in accordance with an exemplary embodiment of the present disclosure.

FIG. 6 is a perspective view of a crossing termination shunt in accordance with an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

To facilitate an understanding of embodiments, principles, and features of the present disclosure, they are explained hereinafter with reference to implementation in illustrative embodiments. In particular, they are described in the context of crossing termination shunts, utilized for example within a railroad crossing control system.

The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present disclosure.

FIG. 1 illustrates a schematic view of a grade crossing warning system 100 at a location in which a road 20 crosses train track 22. The train track 22 includes two rails 22 a, 22 b and a plurality of ties (not shown in FIG. 1 ) that support the rails. The rails 22 a, 22 b are shown as including inductors 22 c. The inductors 22 c are not separate physical devices but rather are shown to illustrate the inherent distributed inductance of the rails 22 a, 22 b.

A track circuit 40 may comprise a transmitter 43 connected across the rails 22 a, 22 b on one side of the road 20 and a receiver 44 connected across the rails 22 a, 22 b on the other side of the road 20. Although the transmitter 43 and receiver 44 are connected on opposite sides of the road 20, those of skill in the art will recognize that the components of the transmitter 43 and receiver 44 other than the physical conductors that connect to the track 22 are often co-located in an enclosure (which is sometimes referred to in the railroad industry as a bungalow) located on one side of the road 20.

The transmitter 43 and receiver 44 may be connected to a control unit 44A, which may also be located in the aforementioned enclosure. The control unit 44A may be connected, and may include logic, for controlling warning devices 47 at the crossing 20. The control unit 44A may also include logic (which may be implemented in hardware, software, or a combination thereof) for calculating train speed and constant warning time signals for controlling the warning devices 47.

Also shown in FIG. 1 are a pair of crossing termination shunts 200, one on each side of the road 20 at a desired approach distance. The crossing termination shunts 200 may also be referred to as simply shunts. The shunts 200 may be installed in the gravel ballast of the railroad track 22. For security purposes, the shunts 200 may be completed covered with the gravel ballast and only the connecting wires are visible. In another example, instead of installing the shunts 200 in the gravel ballast, the shunts 200 may be installed in a separate shunt enclosure that is in proximity to the railroad tracks.

The shunts 200 may be simple conductors or may be tuned AC circuits configured to shunt a particular frequency being transmitted by the transmitter 43. The transmitter 43 may be configured to transmit a constant current AC signal at a particular frequency, which may be in the audio frequency range, such as between 50 Hz and 1000 Hz. The receiver 44 may measure the voltage across the rails 22 a, 22 b, which (because the transmitter 43 generates a constant current) is indicative of the impedance and hence the inductance of the circuit formed by the rails 22 a, 22 b and shunts 200.

When a train heading toward the road 20 crosses one of the shunts 200, the train's wheels and/or axles act as shunts which essentially shorten the length of the rails 22 a, 22 b, thereby lowering the inductance and hence the impedance and voltage. Measuring a change in the impedance indicates the distance of the train and measuring the rate of change of the impedance (or integrating the impedance over time) allows a speed of the train to be determined. As the train moves toward the road 20 from either direction, the impedance of the circuit will decrease, whereas the impedance will increase as the train moves away from the receiver 44/transmitter 43 toward the shunts 200.

The termination shunts 200 include for example hardwire shunts, wide band shunts, or narrow band shunts. Depending on a frequency used and existing ballast conditions at a specific grade crossing, an efficacy of a termination shunt may vary. For example, lower frequencies, e.g. 86 Hz, can create situations where an approach is not fully terminated by the termination shunt, resulting in the system, e.g. predictor and/or motion system, to look beyond the intended point of termination.

A not fully terminated approach circuit may be addressed by “doubling” termination shunts at the crossing, i.e. installing a second shunt with the same frequency. Depending on the location, customers either (1) use a shunt enclosure that houses the termination shunts, or (2) the termination shunts are buried in the ballast between the ties. In case of (1) the retrofit installation of a second shunt is simple, if the existing enclosure is large enough. No additional rail connections are necessary. In case of (2), the retrofit installation will require an additional set of rail connections.

FIG. 2 and FIG. 3 are schematic diagrams illustrating a first and a second embodiment of a combined crossing termination shunt 200 in accordance with an exemplary embodiment of the present disclosure. The crossing termination shunt 200 is configured as combined crossing termination shunt and may be utilized in connection with the grade crossing warning system 100 as described with reference to FIG. 1 .

In an exemplary embodiment, the crossing termination shunt 200 combines components and elements of multiple termination shunts, specifically into a single shunt housing or enclosure. The provided combined termination shunt 200 has the same look and feel as a regular shunt, but the improved termination efficacy of two or more discrete shunts. Thus, instead of installing multiple separate shunts, the combined termination shunt 200 provides full and reliable termination of the approach circuit.

With reference to FIG. 2 and FIG. 3 , the termination shunt 200 comprises a housing 210, a first printed circuit board (PCB) 220 comprising first circuitry 222 and first rail terminals 224, a second printed circuit board (PCB) 230 comprising second circuitry 232 and second rail terminals 234. Simply put, the first PCB 220 with its components 222, 224 forms a first shunting device, and the second PCB 230 with its components 232, 234 forms a second shunting device, wherein the combined termination shunt 200 incorporates the shunting devices into one termination shunt 200. The first PCB 220 with components 222, 224 and the second PCB 230 with components 232, 234 are positioned inside the housing 210. It should be noted that the combined termination shunt 200 may comprise further PCB s with circuitry and rail terminals, for example a third PCB, according to for example specific requirements of the combined termination shunt 200, i.e. multiple discrete shunts may be formed within the housing 210. The circuitry of a termination shunt, such as circuitry 222, 232, comprises a plurality of inductors and capacitors, the interconnection of which determines a nominal frequency of the shunt.

In another example, the termination shunt 200 may comprise one ore more header boards positioned in one end of housing. In this case, the circuitry 222, 232, specifically inductors and capacitors, can be connected to a plurality of header terminals that are mounted on the header board(s). Header terminals are enclosed by a cover to seal the interior of housing from the elements. The frequency of the shunt can be determined and varied by (different) connection(s) between the header terminals.

The housing 210 is formed or shaped such that it appropriately encloses the shunting components in a space saving manner. The housing 210 can comprise plastic materials and can be made for example from polyvinyl chloride (PVC).

Further, the combined termination shunt 200 comprises wire connections 240, wherein a pair of wire connections 240 is attached to the first rail terminals 224 and the second rail terminals 234. The pair of wire connections 240 is attached in parallel to the first rail terminals 224 and the second rail terminals 234.

In accordance with the first embodiment illustrated in FIG. 2 , the wire connections 240 are attached to the rail terminals 224, 234 within the housing 210, wherein the wire connections, specifically the other ends of the connections, extend outwardly through the housing 210. Specifically, first sections 240A of the wire connections are attached to the first rail terminals 224, and second sections 240B are attached to the second rail terminals 234. Further, the second sections 240B of the wire connections are coupled with the first sections 240A internally, e.g. inside the housing 210.

The ends extending outwardly through the housing 210 are configured to be attached/coupled to rails of railroad tracks. Seen from an outside, the combined termination shunt 200 looks like a regular shunting device, but includes multiple shunting components equivalent of two or more discrete shunts, and the wire connections 240A, 240B to the multiple discrete shunts, i.e. PCBs 220, 230, are within the housing 210.

In accordance with the second embodiment illustrated in FIG. 3 , the wire connections 240 are attached to the rail terminals 224, 234 within the housing 210, wherein the wire connections, specifically the other ends of the connections, extend outwardly through the housing 210. First sections 240A of the wire connections are attached to the first rail terminals 224, and second sections 240B are attached to the second rail terminals 234. Further, the second sections 240B of the wire connections are coupled to first sections 240A externally, e.g. outside of the housing 210.

Both embodiments according to FIG. 2 and FIG. 3 illustrate a combined termination shunt 200 wherein the first PCB 220 and the second PCB 230 are each embodied as a separate, individual PCB.

FIG. 4 and FIG. 5 are schematic diagrams illustrating a third and a fourth embodiment of a combined crossing termination shunt 200 in accordance with an exemplary embodiment of the present disclosure. The crossing termination shunt 200 is configured as combined crossing termination shunt and may be utilized in connection with the grade crossing warning system 100 as described with reference to FIG. 1 .

The third and fourth embodiment according to FIG. 4 and FIG. 5 illustrate a combined termination shunt 220, wherein the first PCB 220 and the second PCB 230 are embodied as a common, single PCB.

Further, the combined termination shunt 200 comprises wire connections 240, wherein a pair of wire connections 240 is attached to the first rail terminals 224 and the second rail terminals 234. The pair of wire connections 240 is attached in parallel to the first rail terminals 224 and the second rail terminals 234.

In accordance with the first embodiment illustrated in FIG. 4 , the wire connections 240 are attached to the rail terminals 224, 234 within the housing 210, wherein the wire connections, specifically the other ends of the connections, extend outwardly through the housing 210. Specifically, first sections 240A of the wire connections are attached to the first rail terminals 224, and second sections 240B are attached to the second rail terminals 234. Further, the second sections 240B of the wire connections are coupled to first sections 240A internally, e.g. inside the housing 210.

In accordance with the second embodiment illustrated in FIG. 5 , the wire connections 240 are attached to the rail terminals 224, 234 within the housing 210, wherein the wire connections, specifically the other ends of the connections, extend outwardly through the housing 210. First sections 240A of the wire connections are attached to the first rail terminals 224, and second sections 240B are attached to the second rail terminals 234. Further, the second sections 240B of the wire connections are coupled to first sections 240A externally, e.g. outside of the housing 210. It should be noted that many different locations/configurations of the rail terminals 224, 234 are possible, some of which are illustrated in FIGS. 2-5 (rail terminals 224, 234 at different sides of the PCBs 220, 230).

In an exemplary embodiment of the present disclosure and with reference to the embodiments of FIGS. 2-5 , the first circuitry 222 and second circuitry 232 are configured for a same frequency. In an exemplary embodiment, the first circuitry 222 and the second circuitry 232 are configured for a frequency between 50 Hz and 1000 Hz. Specifically, the circuitries 222, 232 may be configured for a frequency of 86 Hz. In particular lower frequencies, e.g. 86 Hz, may create situations where an approach is not fully terminated by the termination shunt. Lower frequency shunts may be embodiment as so-called narrow band shunts. However, it should be noted that the termination shunt 200 may be embodied for many different frequencies, and/or may be embodied as narrow band shunt or wide band shunt.

FIG. 6 is a perspective view of a crossing termination shunt in accordance with an exemplary embodiment of the present disclosure, such as for example combined termination shunt 200.

The shunt 200 includes an outer housing 210 which has a cap 212 at one end through which extends the pair of electrical wire connectors 240, each of which will be connected to one of the rails of a respective section of track. Within housing 210 are the PCBs 220, 230, each of which has a pair of rail terminals 224, 234 at one end, wherein wire connectors 240 are coupled to the terminals 224, 234. Further illustrated are a plurality of header terminals 252 each of which are mounted on header board(s) 250 positioned in one end of housing 210. The header terminals 252 are enclosed by a cover 214 which may be formed of a rubber or rubberlike material so as to seal the interior of housing 210 from the elements. It should be noted that although only PCB 220 and terminals 224 are shown, the combined termination shunt 200 includes at least another PCB 230 with circuitry 232 and terminals 234. Further, it should be noted that the shunt 200 as illustrated in FIG. 6 may be embodied as described with reference to FIGS. 2-5 .

In use, the shunt 200 may be buried in ballast between rails and the wire connectors 240 may be connected to adjacent rails. In another example, instead of burying the shunts 200 in the gravel ballast, the shunts 200 may be installed in a separate shunt enclosure that is located in proximity to the railroad tracks. Jumpers may be used to connect certain designated header terminals which will determine the nominal frequency of the shunt. The combined crossing termination shunt 200 provides full and reliable termination shunt functionality by incorporating multiple discrete shunting devices, and thus avoids installation of multiple shunts and multiple sets of track connections. 

1. A combined crossing termination shunt comprising: a housing, a first printed circuit board (PCB) comprising first circuitry and first rail terminals, a second printed circuit board (PCB) comprising second circuitry and second rail terminals, wherein the first PCB and the second PCB are positioned inside the housing, and wherein the first circuitry and the second circuitry are configured for a same frequency.
 2. The combined crossing termination shunt of claim 1, wherein the first PCB and the second PCB are each embodied as a separate, individual PCB, or wherein the first PCB and the second PCB are embodied as a common, single PCB.
 3. The combined crossing termination shunt of claim 1, further comprising wire connections, wherein the wire connections are attached to the first rail terminals and the second rail terminals, and wherein the wire connections extend outwardly through the housing.
 4. The combined crossing termination shunt of claim 1, wherein the wire connections are attached in parallel to the first rail terminals and the second rail terminals.
 5. The combined crossing termination shunt of claim 3, wherein first sections of the wire connections are attached to the first rail terminals and second sections of the wire connections are attached to the second rail terminals, and wherein the second sections are coupled to the first sections inside the housing.
 6. The combined crossing termination shunt of claim 3, wherein first sections of the wire connections are attached to the first rail terminals and second sections of the wire connections are attached to the second rail terminals, and wherein the second sections are coupled to the first sections outside of the housing.
 7. The combined crossing termination shunt of claim 1, wherein the first circuitry and the second circuitry are configured for a frequency between 50 Hz and 1000 Hz.
 8. A railroad crossing control system comprising: a grade crossing predictor system or grade crossing motion system comprising at least one combined crossing termination shunt, the at least one combined crossing termination shunt comprising: a housing, a first printed circuit board (PCB) comprising first circuitry and first rail terminals, a second printed circuit board (PCB) comprising second circuitry and second rail terminals, wherein the first PCB and the second PCB are positioned inside the housing, and wherein the first circuitry and the second circuitry are configured for a same frequency.
 9. The railroad crossing control system of claim 8, wherein the first PCB and the second PCB are each embodied as a separate, individual PCB, or wherein the first PCB and the second PCB are embodied as a common, single PCB.
 10. The railroad crossing control system of claim 8, further comprising wire connections, wherein the wire connections are attached to the first rail terminals and the second rail terminals, and wherein the wire connections extend outwardly through the housing.
 11. The railroad crossing control system of claim 10, wherein the wire connections are attached in parallel to the first rail terminals and the second rail terminals.
 12. The railroad crossing control system of claim 10, wherein first sections of the wire connections are attached to the first rail terminals and second sections of the wire connections are attached to the second rail terminals, and wherein the second sections are coupled to the first sections inside the housing.
 13. The railroad crossing control system of claim 10, wherein first sections of the wire connections are attached to the first rail terminals and second sections of the wire connections are attached to the second rail terminals, and wherein the second sections are coupled to the first sections outside of the housing.
 14. The railroad crossing control system of claim 8, wherein the first circuitry and the second circuitry are configured for a frequency between 50 Hz and 1000 Hz. 